There is Google Docs (registered trademark), for example, as an on-line tool for a plurality of users to collaboratively edit the same editing target through a network such as the Internet.
With Google Docs, a plurality of users (editors) manipulate terminals of the respective users, and thereby can collaboratively edit an editing target held in a server connected to the terminals through a network.
When using Google Docs, each user edits the editing target in the view range of the editing target displayed in the terminal that the user manipulates.
In use of Google Docs, a communication system including, for example, a plurality of terminals and a server communicating with the terminals through a network is used (see for example, Patent Literature 1).